From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753227Ab2FIW7D (ORCPT <rfc822;w@1wt.eu>);
	Sat, 9 Jun 2012 18:59:03 -0400
Received: from mail-we0-f174.google.com ([74.125.82.174]:45884 "EHLO
	mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751899Ab2FIW7B (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Sat, 9 Jun 2012 18:59:01 -0400
Date: Sun, 10 Jun 2012 00:58:56 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Alessio Igor Bogani <abogani@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>, Avi Kivity <avi@redhat.com>,
        Chris Metcalf <cmetcalf@tilera.com>, Christoph Lameter <cl@linux.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Geoff Levand <geoff@infradead.org>,
        Gilad Ben Yossef <gilad@benyossef.com>,
        Hakan Akkan <hakanakkan@gmail.com>, Kevin Hilman <khilman@ti.com>,
        Max Krasnyansky <maxk@qualcomm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Stephen Hemminger <shemminger@vyatta.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sven-Thorsten Dietrich <thebigcorporation@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/2] rcu: Extended quiescent state for adaptive nohz
Message-ID: <20120609225852.GC31957@somewhere.redhat.com>
References: <1338811708-18819-1-git-send-email-fweisbec@gmail.com>
 <20120604181313.GL2490@linux.vnet.ibm.com>
 <CAFTL4hzqa1z4icSBwEqZXLjCrVsG+axm2TaGSaaMXkjazT0Qfw@mail.gmail.com>
 <20120604210709.GO2490@linux.vnet.ibm.com>
 <20120605103055.GA4553@somewhere.redhat.com>
 <20120605234640.GY2388@linux.vnet.ibm.com>
 <20120607142101.GI19842@somewhere.redhat.com>
 <20120607224508.GX19601@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20120607224508.GX19601@linux.vnet.ibm.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Jun 07, 2012 at 03:45:08PM -0700, Paul E. McKenney wrote:
> > I can see you've implemented a version for TinyRCU. Nohz cpusets only work on
> > SMP right now because there must be at least one CPU running with the tick
> > to maintain the timekeeping. I'm pretty confident that one day we'll remove
> > the jiffies and we'll be able to do the whole timekeeping by using the TSC
> > or so. There is quite a way before we reach that though.
> 
> In the meantime, would it make sense to slow the tick rate by a factor
> of 10 or so on that one CPU when nothing else is going on?  Or does
> timekeeping absolutely require running the tick at full speed?

I'm not sure of the possible consequences of that.